Waveguide Photodetector End-Face Geometry for Coupling Tolerance
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Solution Overview
Problem
Waveguide-type semiconductor light receiving elements experience coupling loss due to mode mismatch when the light absorbing layer is butt-jointed to optical waveguides, particularly those formed of silicon layers, leading to inadequate coupling tolerance.
Innovation Solution
A waveguide-type light receiving element with a semi-insulating semiconductor substrate, a light absorbing layer having joint surfaces perpendicular to the substrate, and n-type and p-type semiconductor layers formed laterally with the absorbing layer, where the incident end face has a thickness longer than its width, facilitating improved coupling tolerance with optical waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the light absorbing layer is made thin to improve response speed, then operation speed is improved, but coupling tolerance with optical waveguides deteriorates
Solution Approach 1:
The patent changes the geometric configuration of the incident end face from a conventional square or rectangular shape to a shape where the layer thickness dimension is longer than the layer width dimension. This dimensional reconfiguration allows the thin light absorbing layer to maintain both fast response speed and high coupling tolerance by optimizing the interaction area with optical waveguides in a different dimensional arrangement.
2Adaptability or versatility
If intermediate refractive index layers are added to improve coupling tolerance, then coupling tolerance is improved, but device complexity increases
Solution Approach 1:
The patent extracts and eliminates the intermediate refractive index layers from the conventional structure, achieving coupling tolerance improvement through a different mechanism. By removing these additional layers and instead optimizing the incident end face geometry of the light absorbing layer itself, the invention reduces structural complexity while maintaining or improving coupling tolerance.
3Adaptability or versatility
If the light absorbing layer thickness is increased to improve coupling tolerance, then coupling tolerance is improved, but response speed deteriorates
Solution Approach 1:
The patent resolves this contradiction by changing the dimensional relationship at the incident end face, making the layer thickness longer than the layer width. This allows the light absorbing layer to achieve effective coupling with optical waveguides through optimized geometric configuration rather than increased thickness, thereby maintaining fast response speed while improving coupling tolerance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances coupling tolerance and light receiving efficiency by allowing for precise alignment and increased operation speed, even with optical waveguides of varying diameters, such as silicon layers, while maintaining high accuracy in mounting.
Implementation Method 1
a light absorbing layer that is formed on one main surface of the semiconductor substrate and has a pair of joint surfaces perpendicular to the one main surface of the semiconductor substrate and an incident end face on which light is incident
Data Source
AI summary
An optical receiver includes: a support base; a waveguide-type light receiving element fixed to a surface of the support base; and an optical circuit element fixed to the surface of the support base, wherein the waveguide-type light receiving element includes: a semi-insulating semiconductor substrate; a light absorbing layer formed on one main surface of the semiconductor substrate and has a pair of joint surfaces perpendicular to the one main surface of the semiconductor substrate and an incident end face on which light is incident and which has facing end sides of the joint surfaces as a pair of opposite sides, the incident end face having a layer thickness longer than a layer width; an n-type semiconductor layer joined to one of the joint surfaces of the light absorbing layer, and a p-type semiconductor layer joined to the other of the joint surfaces of the light absorbing layer.